Photolithographic production of microprotrusions for use as a space separator in an electrical storage device

ABSTRACT

The present invention relates to a photolithographic method to produce multiple, electrically insulating microprotrusions on an electrically conducting substrate to produce and maintain substantially uniform space separation between the substrates which act as electrodes in a double layer capacitor or battery configuration. Preferably, the electrically insulating microprotrusions are an organic photocurable epoxide polymer, a photocurable acrylic polymer or combinations thereof.

RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. applicationSer. No. 958,506, now abandoned filed Oct. 7, 1992 and U.S. patentapplication Ser. No. 947,294, filed Sep. 18, 1992, now U.S. Pat. No.5,464,453, which are both incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a method to produce an electricallyinsulating space separator between two electrically conducting surfacesby photolithographic production of microprotrusions e.g., epoxy, oracrylic onto a substrate. This method produces multiple micro-sizedstandoffs (protrusions) useful in electronic devices to maintain smalluniform electrode separations with large (greater than 90%) opencross-sectional area.

2. Background Art and Related Art Disclosures

There has been significant research over the years regarding electricalstorage devices of high energy and power density. The efficientpackaging of the active materials, with minimum wasted volume, isimportant in reaching these goals. The space separating two electrodesin a capacitor or a battery is necessary to electronically insulate thetwo electrodes. However, for efficient packaging, this space or gapshould be a minimum. It would therefore by highly desirable to have amethod to create a space separator or gap that is substantially uniformand of small dimension (less than 5 mil).

A common way to maintain separation between electrodes in an electricalstorage device with an electrolyte present (such as a battery orcapacitor) is by use of an ion permeable electrically insulating porousmembrane. This membrane is commonly placed between the electrodes andmaintains the required space separation between the two electrodes.Porous separator material, such as paper, glass, is useful for thisapplication and is used in aluminum electrolytic and double layercapacitors. However, for dimensions below 1 or 2 mil in separation,material handling is difficult and material strength of the computer isusually very low. In addition, the open cross-sectional areas typical ofthese porous membrane separators are on the order of 50-70%.

A recent review by B. E. Conway in J. Electrochem. Soc., Vol. 138 (#6),p. 1539 (June 1991) discusses the transition from "supercapacitor" to"battery" in electrochemical energy storage. He also identifiesperformance characteristics of various capacitor devices.

D. Craig, Canadian Patent No. 1,196,683, issued in November 1985,discusses the usefulness of electric storage devices based onceramic-oxide coated electrodes and pseudo-capacitance. However,attempts to utilize this disclosure have resulted in capacitors whichhave inconsistent electrical properties and which are often unreliable.These devices cannot be charged to 1.0 V/cell and have large,unsatisfactory leakage currents. Furthermore, these devices have a verylow cycle life. In addition, the disclosed packaging is inefficient.

M. Matroka and R. Hackbart, U.S. Pat. No. 5,121,288, issued Jun. 9,1992, discusses a capacitive power supply based on the Craig patentwhich is not enabling for the present invention. A capacitorconfiguration as a power supply for a radiotelephone is taught; however,no enabling disclosure for the capacitor is taught.

J. Kalenowsky, U.S. Pat. No. 5,063,340, issued Nov. 5, 1991, discusses acapacitive power supply having a charge equalization circuit. Thiscircuit allows a multicell capacitor to be charged without overchargingthe individual cells. The present invention does not require a chargeequalization circuit to fully charge a multicell stack configurationwithout overcharging an intermediate cell.

H. Lee, et al. in IEEE Transactions on Magnetics, vol 25 (#1), p.324(January 1989) and G. Bullard, et al., in IEEE Transactions onMagnetics, vol.25 (#1) p. 102 (January 1989) discuss the pulse powercharacteristics of high-energy ceramic-oxide based double-layercapacitors. In this reference various performance characteristics arediscussed, with no enabling discussion of the construction methodology.The present invention provides a more reliable device with moreefficient packaging.

Carbon electrode based double-layer capacitors have been extensivelydeveloped based on the original work of Rightmire U.S. Pat. No.3,288,641. A. Yoshida et al., in IEEE Transactions on Components,Hybrids and Manufacturing Technology, Vol. CHMT-10, #1,P-100-103 (March1987) discusses an electric double-layer capacitor composed of activatedcarbon fiber electrodes and a nonaqueous electrolyte. In addition, thepackaging of this double-layer capacitor is revealed. These devices areon the order of 0.4-1 cc in volume with an energy storage capability ofaround 1-10 J/cc.

T. Suzuki, et al., in NEC Research and Development, No. 82, pp. 118-123,July 1986, discloses improved self-discharge characteristics of thecarbon electric double-layer capacitor with the use of porous separatormaterials on the order of 0.004 inches thick. An inherent problem ofcarbon based electrodes is the low conductivity of the materialresulting in a low current density being delivered from these devices. Asecond difficulty is that the construction of multicell stacks is notdone in a true bipolar electrode configuration. This results ininefficient packaging and lower energy and power density values.

Additional references of interest include, for example:

The state of solid state micro power sources is reviewed by S. Sekido inSolid State Ionics, Vol. 9, 10, pp. 777-782 (1983). M. Pham-Thi et al.in the Journal of Materials Science Letters, Vol. 5, p. 415 (1986)discusses the percolation threshold and interface optimization in carbonbased solid electrolyte double-layer capacitors.

Various disclosures discuss the fabrication of oxide coated electrodesand the application of these electrodes in the chlor-alkali industry forthe electrochemical generation of chlorine. See for example: V. Hock, etal. U.S. Pat. No. 5,055,169 issued Oct. 8, 1991; H. Beer U.S. Pat. No.4,052,271 issued Oct. 4, 1977; and A. Martinsons, et al. U.S. Pat. No.3,562,008 issued Feb. 9, 1971. These electrodes, however, in general donot have the high surface areas required for an efficient double-layercapacitor electrode.

Polymeric ion permeable porous separators have been used in carbondouble layer capacitors as discussed by Sanada et al. in IEEE,pp.224-230, 1982 and Suzuki et al. in NEC Research and Development, No.82, pp. 118-123, July 1986. These type of separators suffer from theproblem of a small open area which leads to increased electricalresistance.

A method of using photoresist to fill voids of an electricallyinsulating layer to prevent electrical contact between two electrodelayers for use as a solar cell is disclosed by J. Wilfried in U.S. Pat.No. 4,774,193, issued Sep. 27, 1988.

A process of creating an electrolytic capacitor with thin spacer using aphotosensitive polymer resin solution is disclosed by Maruyama et al inU.S. Pat. No. 4,764,181 issued Aug. 16, 1988. The use of solutionapplication methods described in a porous double-layer capacitorelectrode would result in the undesirable filling of the porouselectrode.

U.S. Patents of general interest include U.S. Pat. Nos. 3,718,551;4,052,271; and 5,055,169.

None of these references individually or collectively teach or suggestthe present invention.

All of the applications, patents, articles, references, standards, etc.cited in this application are incorporated herein by reference in theirentirety.

It would be very useful to have a method to produce a reliable smallspace separation between electrodes in electrical storage devices with alarge open cross-sectional area. It is, therefore, an object of thepresent invention to provide efficient packaging of an electricalstorage device by reducing the gap between the anode and cathode and toreduce the electrical resistance of the ionically conducting electrolyteby providing large open cross-sectional areas of about 95-98%. Thepresent invention provides such an improved method and improved devicewith energy densities of at least 20-90 J/cc, each cell of the capacitoror battery is charged to about 1 volt per cell, the voltage in each cellis essentially additive to produce devices of low to high charge storagecapacity, and the devices operate in a double layer manner.

SUMMARY OF THE INVENTION

The present invention relates to a photolithographic method to producemicroprotrusions which are uniform in height on a substrate to maintainspace separation in an electrical storage device, which methodcomprises:

(a) obtaining an unexposed photoresist film which is essentially inertto subsequent electrolyte conditions and is electrically insulating whencured:

(b) obtaining a thin electrode material comprising a thin flatelectrically conducting metal sheet center coated on one or both flatsides with electrically conducting porous metal oxide or electricallyconducting carbon;

(c) applying the photoresist film to one or to both flat sides of theelectrode material;

(d) placing a mask having a plurality of small holes over thephotoresist;

(e) exposing the photoresist to a light source of an intensity and for atime effective to substantially cure the light exposed photoresistmaterial through the holes in the mask to create cured microprotrusionswhich are uniform in height, removing the mask;

(f) developing the photoresist film to leave the cured microprotrusionswhich are uniform in height on the surface of the electrode material andto remove unreacted film;

(g) further curing the remaining exposed material whereby themicroprotrusions essentially retain their shape and dimensions.

In one aspect, the present invention related to an improved method toproduce a dry preunit (10) of an electrical storage device for storageof electrical charge in a condition for contact with a nonaqueous oraqueous electrolyte, which method comprises:

(a) preparing a thin in thickness substantially flat sheet ofelectrically conducting support material coated on each flat side withthe same or different thin layer of a second electrically conductingmaterial having a high surface area, optionally with the provision thatboth flat sides of the electrically conducting support is a sheet havingthe perimeter edge surfaces either:

(i) having a thin layer of second high surface area electricallyconducting material,

(ii) are partly devoid of second high surface area electricallyconducting material, or

(iii) are devoid of second high surface area electrically conductingmaterial;

(b) creating an ion permeable or semipermeable space separator which isstable to the aqueous or non-aqueous electrolyte which is obtained by:

(i) depositing substantially uniform in height groups of electricallyinsulating microprotrusions stable to the aqueous or non aqueouselectrolyte, on the surface of at least one side of the thin layer ofthe second electrically conducting material,

(ii) placing a thin precut ion permeable or semipermeable separator onone surface of the second electrically conducting material, or

(iii) casting an ion permeable or semipermeable thin layer on thesurface of at least one side of the electrically conducting material, or

(iv) creating a thin air space as separator;

(c) contacting the perimeter edge surface of one or both sides of thethin sheet of step (b) with one or more thin layers of synthetic organicpolymer as a gasket material selected from the group consisting of athermoplastic and a thermoset polymer;

(d) placing on or within the gasket material and optionally across thethin sheet at least one thin cord of a different material which cord hasa higher melting point (Tm) than the gasket polymer material and doesnot melt, flow, or permanently adhere to the gasket under the processingconditions;

(e) producing a repeating layered stack of the thin flat articles ofsheet coated with metal oxide and separator produced in step (d)optionally having the end sheets consisting of a thicker support;

(f) heating the stack produced in step (e) at a temperature and appliedpressure effective to cause the synthetic gasket material to flow, toadhere to, and to seal the edges of the stack creating a solid integralstack of layers of alternating electrically conductive sheet coated withsecond electrically conducting material and the ion permeable separator,optionally such that the gasket material creates a continuous integralenclosure;

(g) cooling the solid integral stack of step (f) optionally under slightpressure in an inert gas; and

(h) removing the at least one thin cord of different material betweeneach layer creating at least one small opening between the layers ofelectrically conducting sheet coated with second electrically conductingmaterial.

In one embodiment the exterior end sheets have only one side coated withsecond high surface area electrically conducting material.

In another aspect, the present method includes a method to produce a drypreunit of a capacitor for storage of electrical charge, which methodcomprises:

(a) obtaining a thin thickness flat metal sheet support wherein themetal is selected from titanium, zirconium, iron, copper, lead, tin,zinc or combinations thereof, having a thickness of between about 0.1and 10 mil coated on each flat surface with a thin layer of at least onemetal oxide having a high surface area independently selected from metaloxides of the group consisting of tin, lead, vanadium, titanium,ruthenium, tantalum, rhodium, osmium, iridium, iron, cobalt, nickel,copper, molybdenum, niobium, chromium, manganese, lanthanum or lanthanumseries metals or alloys or combinations thereof, possibly containingsmall percentage of additives to enhance electrical conductivity,

wherein the thin metal oxide layer has a thickness of between about 0.1and 100 microns,

optionally with the provision that both flat surfaces of theelectrically conducting sheet have the perimeter edge surfaces devoid ofmetal oxide;

(b) creating an ion permeable space separator which is stable to theaqueous or non-aqueous electrolyte selected from:

(i) depositing by screen printing or photolithography a substantiallyuniform in height array of electrically insulating microprotrusionswhich are stable to an aqueous or non-aqueous electrolyte having aheight of between about 0.1 and 10 mil on the surface of one or bothsides of the thin layer of metal oxide,

(ii) placing a thin precut ion permeable electrically insulatingseparator having a thickness of between about 0.1 and 10 mil on one flatsurface of the metal oxide layer;

(iii) casting an ion permeable or semipermeable separator having athickness of between about 0.1 and 10 mil on at least one surface of thesecond electrically conducting material; or

(iv) creating a thin air space as a separator;

(c) contacting the perimeter edge surface of one or both sides of thethin electrically conducting sheet of step (b) with one or more thinlayers of synthetic organic polymer as a gasket material wherein thepolymer is selected from polyimides, TEFZEL®, polyethylenes,polypropylenes, other polyolefins, polysulfone, other fluorinated orpartly fluorinated polymers or combinations thereof;

(d) placing on or within the gasket material and optionally across thethin flat sheet at least one thin cord of a different material which hasa higher melting temperature (T_(m)) than the polymeric gasket material,which cord does not melt, flow or adhere to the gasket material underthe processing conditions described herein;

(e) assembling a repeating layered stack of the thin flat articles ofsheet coated with metal oxide and separator produced in step (d)optionally having end sheets having only one side coated and/or beingmade of thicker support material;

(f) heating the layered stack of step (e) at 0° to 100° C. greater thanT_(m) causing the gasket material to flow, to adhere to, and to seal theedges of the layered stack creating a solid integral layered stack ofsheet and separator optionally enclosing the stack in an integralpolymer enclosure;

(g) cooling to ambient temperature the solid integral stack of step (f)in an inert environment; and

(h) removing the at least one thin cord between each layer creating atleast one small opening between the electrode layers.

In other aspects, the present invention relates to the improved storagedevices produced by the above cited methods when the electrodes arefurther contacted with an aqueous or non-aqueous electrolyte optionallydeoxygenated.

Preferably the insulator material is an organic epoxy polymer, acrylicpolymer or combinations thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of the exterior of the dry preunit (10)with the cords present (17A) and after being pulled out (17C).

FIG. 2 is a cross-sectional view of the dry preunit along line 2--2showing the edge of the dry preunit prior to heating to fuse thegaskets. For depiction purposes only the cords have been removed in allexcept one case (17A). The end sheet support (11 and 11A) as well as thecoating (12 and 12A) are also depicted.

FIG. 2A is a cross-sectional view of the dry preunit along line 2A--2Ashowing the central area of the dry preunit prior (again, for depictionpurposes only most of the cords have been removed) to heating to fusethe gasket material (14C and 14D). The electrode support material (15)and the coating (16 and 16A) for the internal bipolar electrodes aredepicted. The open space between electrode surfaces optionally containsmicroprotrusions, a thin porous film, or a cast porous film as aseparator.

FIG. 3 is a schematic representation of an exploded view of the drypreunit with cords present in the typical staggard configuration (17A,17B, and 17C). Bipolar electrodes consisting of a support (15) andcoating (16 and 16A) with microprotrusions (13) are depicted with gasketmaterial (14A, 14B, 14C and 14D). The end plate assembly (18A and 18B)are depicted with coating on only one side.

FIG. 4 is a schematic of the steps in the fabrication of the drypre-unit.

FIGS. 5 and 5A are scanning electron microscope (SEM) pictures of theelectrode surfaces having microprotrusions at 16 power and 65 power,respectively.

FIGS. 6 (at 16 power) and 6A (at 65 power) are scanning electronmicroscope (SEM) pictures of the stacked device depicting the tabs 17Aand fillports 17D of the dry preunit.

FIG. 7 is a schematic representation of the method to produce themicroprotrusions of the present invention.

FIG. 8 is a photograph of the surface of the electrode showing themicroprotrusion pattern formed at 8.3 power magnification.

FIG. 9 is a photograph at a top view of the surface of the electrodeshowing the micro protrusion pattern formed at 20.6 power magnification.

FIG. 10 is a schematic representation of the hot rollers used forlaminating the photoresist to the electrode component prior tophotolithography.

FIG. 11 shows a schematic representation of a mask placed over thephotoresist.

FIG. 12 shows a schematic representation of the exposure of theunprotected portions of the photo resist to cause reaction.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

As used herein:

"Cord" or "tab" refers to the thin strips of material included in themethod of manufacture of the dry preunit. The removal of the cordproduces the open fill ports.

"Electrically conducting support material" refers to any electricallyconducting metal or metal alloy, electrically conducting polymer,electrically conducting ceramic, electrically conducting glass, orcombinations thereof. Metals and metal alloys are preferred forproducing stock units. The support material should have a conductivityof greater than about 10⁻⁴ S/cm.

"Photoresist" is any photo curable material. Usually it is an epoxide oracrylate or combinations thereof.

"ConforMASK" is a negative working photopolymer available commerciallyfrom Dynachem of Tustin, Calif.

This polymer should be used at 50% or less relative humidity.

"Epoxy" refers to the conventional definition of the product which is anepoxy resin mixes with a specific curing agent, usually a polyamine, ofpolyepoxide mixed with a polyamine curing agent.

"Metal oxide" refers to any electrically conducting metal oxide.

"Mixed metal oxide" refers to an electrically conducting oxide compoundof two or more metal oxides.

"Second electrically conducting material" (having a high surface area)refers to porous electrode coating which may be of the same or differentcomposition on each side of the support material. Preferred metal oxidesinclude those independently selected from tin, lead, vanadium, titanium,ruthenium, tantalum, rhodium, osmium, iridium, iron, cobalt, nickel,copper, molybdenum, niobium, chromium, manganese, lanthanum, orlanthanum series metals or alloys or combinations thereof, and possiblycontaining additives like calcium to increase electrical conductivity.

"Support" refers to the electrically conducting metal, alloy, ceramic orthe like.

The focus of the present invention is to produce a series ofmicroprotrusions on the surface, or alloys thereof. The substrate isusually in the shape of a thin metal plate as is conventional in thecapacitor art.

Referring to FIGS. 1 to 5, a general description for the improved methodto produce the dry pre-unit 10 is as follows:

(A) Support Material Preparation

The electrode support (11, 11A and 15) is optionally etched or cleanedby a variety of conventional pickling and cleaning procedures.

In some experiments, if the metal surface is not etched it is toosmooth. This smooth surface sometimes causes inadequate adhesion of theporous coating. The etch creates a suitable rough surface.

1. Wet Etching--A preferred procedure is contact of the metal supportwith aqueous inorganic strong acid, e.g. sulfuric acid, hydrochloricacid, hydrofluoric acid, nitric acid, perchloric acid or combinationsthereof. The etching is usually performed at elevated temperatures of50° to 95° C. (preferably 75° C.) for about 0.1 to 5 hr (preferably 0.5hr.) followed by a water rinse. Room temperature acid etching ispossible. An alkaline etch or an oxalic acid etch may also used.

2. Dry Etching--The roughened support surface is obtained by sputtering,plasma treatment, and/or ion milling. A preferred procedure is Ar RFsputter etching at between around 0.001 and 1 torr with about 1 KeVenergy at 13.5 Mhz. Commonly, 0.1-10 watts/cm2 power densities for about1-60 minutes are used to clean and roughen the surface. Anotherprocedure is to plasma etch the support with a reactive gas such asoxygen, tetrafluoromethane, and/or sulfurhexafluoride at around 0.1-30torr for about 1-60 min.

3. Electrochemical Etching--The roughened surface is obtained byelectrochemical oxidation treatment in a chloride or fluoride solution.

(B) Coating of Support Material

The high surface area electrically conducting coating material (12, 12A,16 and 16A) is applied onto the support material.

1. Solution Methods--The porous coating material may originate fromvarious reactive precursors in a solution or of a sol-gel composition.Numerous methods of application of these precursor compositions arefeasible; but not limited to the following. A curing and/or pyrolysisprocess usually is performed to form the coating on the support.Pyrolysis of the metal salts is usually done in a controlled atmosphere(nitrogen, oxygen, water, and/or other inert and oxidative gasses) bymeans of a furnace and/or an infrared source.

(a) Dip Coating--The support is dipped into a solution or sol-gel,coating the support with a precursor coating, and subsequently cured bypyrolytic and other methods. Optionally, this process may be repeated toincrease layer thickness. A preferred procedure is dipping the supportmaterial into a metal chloride alcohol solution followed by pyrolysis atbetween about 250° and 500° C. for 5-20 min in a 5-100% oxygenatmosphere. This process is repeated until the desired weight of coatingis obtained. A final pyrolysis treatment at 250°-450° C. is done for1-10 hrs. Typically about 1-30 mg/cm² of coating is deposited onto asupport for a capacitance density of around 1-10 F per a squarecentimeter electrode cross-sectional area. Another procedure is tocreate a sol-gel solution with ruthenium, silicon, titanium and/or othermetal oxides and coat the support as above. By adjusting the Ph, waterconcentration, solvent, and/or the presence of additives like oxalicacid, formamide, and/or surfactants the discharge frequencycharacteristics of the coating may be adjusted.

(b) Spray Coating--The coating solution is applied to the support by aspray method, cured, and optionally repeated to increase the thickness.A preferred procedure is to apply the coating solution to the substrateat a temperature of 0°-150° C. by means of an ultrasonic or other spraynozzle with a flow rate of around 0.1-5 ml/min in a carrier gas composedof nitrogen, oxygen and/or other reactive and inert gases. The coatingcharacteristics can be controlled by the partial pressure of oxygen andother reactive gasses.

(c) Roll Coating--The precursor coating is applied by a roll coatingmethodology, cured, and optionally repeated to increase the thickness.The coatings used for dip coating are usable here.

(d) Spin Coating--A spin coating methodology is used to apply theprecursor coating, and optionally repeated.

(e) Doctor Blading--A doctor blading methodology is used to apply theprecursor coating, and optionally repeated.

2. Electrophoretic Deposition--The porous coating or precursor coatingis applied to the support by electrophoretic deposition techniques, andoptionally repeated.

3. Chemical Vapor Deposition--The porous coating or precursor coatingmay be applied by chemical vapor deposition techniques.

(C) Electrode Pretreatment

It has been found that a number of pretreatments (conditioning) orcombinations thereof are useful to improve the electricalcharacteristics of the coating (e.g. electrochemical inertness,conductivity, performance characteristics, etc.). These treatmentsinclude for example:

1. Steam--The coated electrode is contacted with water saturated steamin a closed vessel at between 150° and 325° C. for between 1 to 6 hr.under autogenic pressure.

2. Reactive Gas The coated electrode is contacted one or more times witha reactive gas such as oxygen, ozone, hydrogen, peroxides, carbonmonoxide, nitrous oxide, nitrogen dioxide, or nitric oxide at betweenambient temperature and 300° C. at a reduced pressure or under pressure.A preferred procedure is to contact the coated electrode with flowingozone at between about 5-20 weight percent in air at between ambient and100° C. and 0.1-2000 torr pressure for 0.1-3 hours.

3. Supercritical Fluid--The coated electrode is contacted with asupercritical fluid such as carbon dioxide, organic solvent, and/orwater. A preferred procedure is treatment with supercritical water orcarbon dioxide for 0.1-5 hrs by first raising the pressure then thetemperature to supercritical conditions.

4. Electrochemical The coated electrode is contacted with an anodiccurrent sufficient to evolve oxygen gas and subsequently with a cathodiccurrent. In one embodiment the electrode is contacted with 10 mA/cm² insulfuric acid for about 5 min, to evolve oxygen gas. The electrode isthen switched to a cathodic current and the open circuit potential isdriven back to a potential of about 0.5 V (vs. NHE) with out hydrogengas evolution.

5. Reactive liquid The coated electrode is contacted with an oxidizingliquid such as aqueous solutions of hydrogen peroxide, ozone, sulfoxide,potassium permanganate, sodium perchlorate, chromium(VI) species and/ orcombinations thereof at temperatures around ambient to 100° C. for 0.1-6hrs. A preferred procedure uses a 10-100 mg/l aqueous solution of ozoneat 20°-50° C. for around 0.5-2 hrs. followed by an aqueous wash. Anadditional procedure is to treat the coated electrode in a chromate ordichromate solution.

(D) Spacing between Electrodes

A number of methods are available to obtain electrical insulation andproperly defined spacing between the electrodes. These methods include,for example:

1. Microprotrusions--The separator between the electrodes is a matrix ofsmall (in area and height) protrusions (13) on the surface of at leastone side of the electrode. These microprotrusions which are uniform inheight may be composed of thermosets, thermoplastics, elastomers,ceramics, or other electrically insulating materials. Several methods ofapplying these microprotrusions are included but not limited to:

(a) Screen Printing--The microprotrusions are placed on the electrodesurface by conventional screen printing. Various elastomers, thermosets,and thermoplastics are applied in this way. A preferred procedure is touse an acid resistant epoxy or Viton solution.

(b) Chemical Vapor Deposition--Microprotrusions are also placed on theelectrode surface by depositing silica, titania and/or other insulatingoxides or materials through a mask.

(c) Photolithography--see below.

2. Physically thin separator sheet--The separator between the electrodesis a thin, substantially open structure material such as glass. Apreferred material is 0.001-0.005 inch porous glass sheet available fromWhatman Paper Ltd.

3. Casting a separator--The separator between the porous material isalso obtained by casting a thin, substantially open structure film suchas for example Nafion®, polysulfones, or various aero- and sol-gels.

4. Air space--The separator between the electrodes is also an air spacewhich is subsequently occupied by the non-aqueous or aqueouselectrolyte.

(E) Gasketing

The materials used for the gaskets (14A, 14B, 14C and 14D) at the edgeof the active electrode surface include any organic polymer which isstable in the electrical/chemical environment, and to the processingconditions. Suitable polymers include, for example polyimide, TEFZEL®,polyethylene (high and low density), polypropylene, other polyolefins,polysulfone, other fluorinated or partly fluorinated polymers orcombinations thereof. The gasket may be applied as a preformed material,screen printed, or by other methods.

(F) Cord for Fillport

The cord (17A, 17B and 17C) for the creation of the fillport is of anysuitable material having some specific properties, e.g., it is differentfrom the gasket materials has a higher melting temperature (Tm) than thegasket material and does not melt, flow or adhere to the gasket materialunder the heating conditions described herein. Generally, glass, metal,ceramic, and organic polymers or combinations thereof are used.

(G) Stacking

A stack is created by starting with an endplate and alternating gasketmaterial, cord, electrode, gasket, cord electrode until the desirednumber of cells is created ending with a second endplate and optionallywith a gasket material on the top outside of the stack.

(H) Assembling (heating and cooling)

The stack is heated under pressure to cause reflow of the gasketmaterial, adhering and sealing the perimeter of the electrode materialsto the adjacent electrode in the stack; thereby, creating isolated cellsand an assembled stack unit.

(a) Radio Frequency Induction Heating is used to heat the stack to causereflow of the gasket material.

(b) Radiant Heating is used to uniformly heat the stack to cause reflowof the gasket material. A preferred method is to use 1-100 μm radiationat 0.5-10 watts/cm² for 1-20 min.

(c) Conductive and/or convective heating in a furnace, optionally in aninert atmosphere, is used to heat the stack to cause reflow of thegasket material.

(I) Creating the fillport

The cords are pulled to remove them from the assembled unit to create adry preunit with at least one fillport per a cell.

(J) Post-Conditioning

It has been found that a number of post-conditioning reactive gastreatments of the stack or assembled stack or combinations thereof areuseful to improve the electrical characteristics of the electrode andresulting device. These include either before step (H) and/or after step(I) treatment with hydrogen, nitric oxide, carbon monoxide, ammonia, andother reducing gasses or combinations thereof at between ambienttemperature and the Tm of the gasket material at a reduced pressure orunder pressure.

(K) Filling of Dry Preunit

The dry preunit is filled with an ionically conducting aqueous ornon-aqueous electrolyte.

(L) Sealing of Fillports

The fillports are sealed by reflowing an additional film of polymer thesame or different over the openings to create a device. This is commonlydone with an induction heater, locally heating the film over thefillport opening.

(M) Burn-In

The device is brought to full charge by initially charging the device to0.1 V/cell at a charging current of about 4 mA/cm².

(N) Testing

Termination Methods--Several methods are used to make electricalconnections to Ultracapacitor endplates as described below as examples.

1. Endplate Tabs (60 and 60A). The endplates (18A and 18B) themselveshave been cut to extend out beyond the normal gasket perimeter. Theseextensions allow attachment of a wire or ribbon. Typically, theextension is a stub from which all oxide material is removed down to thebare titanium; 5 mil thick nickel ribbon is spot welded to the stub.

2. Silver Epoxy The oxide coating is removed from the exposed faces ofthe endplates or the endplates may be coated only on one side. Cleannickel foil leads make electrical connection to the exposed faces bybonding them together with a conductive silver epoxy.

3. Lugs Threaded titanium nuts are welded to the thick titaniumendplates before coating. Electrical connection to the titanium nuts isachieved by screw attachment.

4. Press Contacts The oxide is removed or the endplates may be coatedonly on one side from the exposed side of the endplates before assemblyinto the device stack. The bare titanium is reversed sputtered to cleanthe surface, being careful not to overheat the substrate. The cleansurface is then sputtered with titanium to lay down a clean adhesionlayer, followed by gold. The gold acts as a low contact resistancesurface to which electrical contact can be made by pressing or by wirebonding.

5. Deposition of a compatible medium such for example aluminum, gold,silver, etc. outside by CVD or other means.

The device resistance is measured at 1 kHz. The device capacitance isdetermined by measuring the coulombs needed to bring the device to fullcharge at a charging rate of around 4 mA/cm² of electrode area. Leakagecurrent is measured as the current needed to maintain a full chargeafter 30 min. of charging.

These devices may be made in various configurations depending on thedesired application. By adjusting the device voltage, cell voltage,electrode area, and/or coating thickness in a rational manner, devicesmade to fit defined specifications can be constructed.

The electrode capacitance density (C' in units of F/cm²) is roughly 1F/cm² for every 10 μm of coating. Therefore, for large capacitancevalues a thicker coat is used. The device capacitance (C) is equal tothe electrode capacitance density times the electrode area (A in unitsof cm²) divided by two times the number of cells (n) (equation 1).

The leakage current (i") is proportional to the electrode area, whilethe equivalent series resistance (ESR) is inversely proportional to theelectrode area (eqn. 2). Typical values for i" are less than 20 μA/cm².

The total number of cells in a device (n) is equal to the cell voltage(V') divided by the total device voltage (V) (eqn. 3). Cell voltages upto about 1.2 V can be used. The device height (h), based on a cell gap(h') and a support thickness (h"), is determined from the number ofcells and the electrode capacitance density in units of cm by equation4.

The device ESR is a function of the number of cells times the cell gap(h') times the resistivity of the electrolyte (r) times a factor ofabout 2 divided by the area (equation 5).

    C=C'A/2n                                                   eqn. 1

    i"∝A∝1/ESR                                   eqn. 2

    n=V/V'                                                     eqn. 3

    h/cm=n(0.002C'+h'+h")                                      eqn. 4

    ESR≈2nh'r/A                                        eqn. 5

Devices are constructed to meet the requirements of various applicationsby considering the voltage, energy, and resistance requirements. Thefollowing examples are not meant to be limiting in any way:

For electric vehicle applications about a 100 KJ to 3 MJ device is used.A large voltage (about 100 to 1000 V) large energy (1-5 F/cm²) storagedevice is used with an electrode area of about 100 to 10000 cm².

For electric heated catalyst applications for reduction of automobilecold start emissions about a 10 to 80 KJ device is used. This device isabout 12 to 50 V constructed with around 100 to 1000 cm² area electrodesof 1-5 F/cm². Optionally, a device consisting of several devices inparallel can be constructed to meet the electrical requirements.

For defibrillator applications about a 200-400 V device with 0.5 to 10cm² area electrodes of 1-3 F/cm² are used.

For uninterruptable power source applications various series/paralleldevice configurations may be used.

The electrode substrate is usually a thin metal sheet such as titanium,zirconium, nickel, aluminum or alloys thereof. The substrate is usuallyin the shape of a thin metal plate, between about 0.1 and 10 mil thickas is conventional in the capacitor art.

The substrate is then coated on one or both sides with a carbon compoundor a porous oxide coating selecting from titanium, ruthenium, tantalum,iridium, or mixtures thereof. This step is accomplished by methodsconventional in the art and described herein. The oxide coating servesas the charge storage area for the device. The thickness of the oxide isusually between about 0.1 and 100 microns.

Alternately, a stacked set of battery electrodes (e.g. lead for leadacid) or electrolytic capacitor electrodes (e.g. alumina and tantalum)may be fabricated.

It is important that the flat surfaces of adjacent substrates do notcontact each other and further be of a uniform separation.

The photoresist is applied either by vacuum lamination using thecommercially available Dynachem ConformMASK film applicator, andDynachem vacuum applicator Model 724/730, or by passing the photo resistfilm and electrode through heated rollers.

Exposure is done using a standard 1-7 kW UV exposure source, such as amercury vapor lamp.

The ConforMask is developed using standard conditions such as 0.5-1.0%sodium or potassium carbonate monohydrate in either a developing tank ora conveyorized aqueous developer. Optionally, after developing theelectrode with microprotrusions may be neutralized in a dilute 10%sulfuric acid solution. This removes all the unwanted unreacted film toleave the reacted microprotrusions adhered to the electrode surface.

To obtain optimum physical and electrical performance properties theresulting material is put through a final curing process involving bothUV irradiation and thermal treatment utilizing conventional UV curingunits and convection air ovens.

The multiple electrodes are assembled to produce for instance acapacitor (10 in-exploded view) as described in detail in pending U.S.Ser. No. 947,294. Referring to FIG. 3, the metal oxide coated (16 and16A) substrate 15 has microprotrusions 13 in place for the desireduniform separation. The photolithographic protrusions have a height ofbetween about 0.1 and 10 mil from the oxide surface. Thephotolithographic protrusions have a top cross-sectional surface area ofbetween 1×10⁻⁸ in² to 0.01 in², preferably between about 1×10⁻⁶ to1×1-⁻⁴ in². Gaskets 14A, 14B and 14C are used to eventually seal theelectrode spaces. Tabs 17A, 17B, 17C make it possible to produce smallopenings into the uniformly formed open space for backfilling withliquid electrolyte.

With regard to FIGS. 7 to 12, the microprotrusions which are uniform inheight accomplish the desired uniform separation.

This electrode 16,15,16A having microprotrusions 13 is then combinedwith others assembled in a wet process or a dry process. If a dryprocess is used, the dry unit is then back filled with electrolyte.

It is important that the cured epoxy does not react with the liquidelectrolyte eventually used in the fabrication of the capacitor havingmultiple layers of electrodes.

It is apparent that from these teachings the following are possible:

Increasing or decreasing the substrate electrode thickness will allow aincrease or decrease in the microprotrusion spacing due to changes insupport requirements.

Other epoxies or epoxy derivatives can be used.

Other microprotrusion pattern elements can be used such as squares,lines, crosses, etc.

UTILITY

The electrical storage devices produced having the claimedmicro-protusions are useful as batteries, capacitors and the like.

The capacitors are useful for example in defibrillators, pacemakers,electric vehicles, portable telephones and the like.

The electrode having the microprotrusions in usually cut to the desireddimensions. Certainly even layered coated electrodes havingmicroprotrusions can be produced. The coated electrode havingmicroprotrusions produced herein is used for example in pending U.S.patent applications Ser. Nos. 947,414, 947,294 and 958,506.

The following Examples are provided to be descriptive and explanatoryonly. They are not to be construed to be limiting in any way.

EXAMPLE 1 Fabrication Of Dry Preunit

(A) Coating Method

The support structure is prepared by etching a 1 mil titanium sheet with35% HNO₃ /1.5% HF at 60° C. for 5 min. The end plates are 5 miltitanium.

The oxide coating solution is 0.2M ruthenium trichloride trihydrate and0.2M niobium pentachloride in tert-butanol (reagent grade).

The etched Ti sheets are dip-coated by immersion into the solution atambient conditions. The coated sheet is submerged into the solution,held for about 1 sec and then removed.

After each coating, the oxide is dried at 70° C. for 10 min, pyrolyzedat 350° C. for 10 min and removed to cool to ambient temperature all inambient atmosphere.

The dip-coating steps are repeated for 10 coats (or any desired number)rotating the Ti sheet so as to dip with alternate sides down.

The fully coated sheet is final annealed at 350° C. for 3 hrs in ambientatmosphere.

(B) Electrode Pretreatment

The coated electrode is contacted with saturated steam in a closedvessel at 280° C. for 3 hrs under autogenic pressure.

(C) Spacing

Microprotrusions are screen printed on one side of the electrode. Theepoxy compound is EP21AR from Masterbond, Hackensack, N.J. See U.S.patent application Ser. No. 947,414, allowed, which is incorporated byreference in its entirety.

The epoxy protrusions are cured at 150° C. for 4 hrs. in air. The coatedelectrodes are next die-stamped to the desired shape.

(D) Gasket

A modified high density polyethylene (HDPE, improved puncture resistanceand adhesion) 1.5 mil thick by 30 mil wide with outside perimeter thesame as that of the electrode is placed on the electrodes on the sameside as the microprotrusions and impulse heat laminated. The HDPE is PJX2242 from Phillips-Joanna of Ladd, Ill.

(E) Cord

One cord (TEFZEL®) 1 mil thick by 10 mil wide is placed across thenarrow dimension of the gasket and electrode surface and aligned betweenmicroprotrusions. The location of the cord is one of three positionscentered, left of center, or right of center.

A second HDPE gasket is placed on the first gasket sandwiching the cordbetween the two gaskets.

The second gasket is impulse heated to adhere to the first gasket and tofix the cord in place.

(F) Stacking

Electrode/microprotrusion/gasket/cord/gasket units are stacked in anonmetallic (ceramic) alignment fixture beginning with a 5 mil end plateunit to the desired number of cells and ending with a plain 5 mil endplate with the cords arranged such that the location is staggered-left,center, right in a three unit repeating cycle (end perspective). Lightpressure is applied to the top of the stack through a ceramic pistonblock to maintain uniform alignment and contact throughout the stack.

(G) Reflow

A radio frequency induction heater (2.5 Kw) is used to heat the stack.The stack was placed centrally in the three turn, 3 inch diameter coiland heated for 90 seconds at a power setting of 32%. The unit is allowedto cool to ambient temperature.

(H) Cord Removal

The cords are removed by pulling the exposed ends to leave the open fillports.

EXAMPLE 2 Fabrication Of Dry Preunit

(A) Coating Method

The support structure is prepared by etching a 1 mil titanium sheet with50% Hcl at 75° C. for 30 min. The end plates are 2 mil titanium.

The oxide coating solution is 0.3M ruthenium trichloride trihydrate and0.2M tantalum pentachloride in isopropanol (reagent grade).

The etched Ti sheets are dip-coated by immersion into the solution atambient conditions. The coated sheet is submerged into the solution,held for about 1 sec and then removed.

After each coating, the oxide is dried at 70° C. for 10 min. in ambientatmosphere, pyrolyzed at 330° C. for 15 min in a 3 cubic feet per hourflow of 50 vol. % oxygen and 50% nitrogen, and removed to cool toambient temperature in ambient atmosphere.

The dip-coating steps are repeated for 30 coats (or any desired number)rotating the Ti sheet so as to dip with alternate sides down.

The fully coated sheet is final annealed at the above conditions for 3hrs.

(C) Spacing

VITON® microprotrusions are screen or photolithographically printed onone side of the electrode screenprinting by adapting U.S. patentapplication Ser. No. 947,414 or by photolithography--U.S. Ser. No.958,506. The VITON® protrusions are cured at 150° C. for 30 min. in air.The coated electrodes are next die-stamped to the desired shape.

(D) Gasket

A modified high density polyethylene (HDPE, improved puncture resistanceand adhesion) 1.0 mil thick by 20 mil wide with outside perimeter thesame as that of the electrode is impulse heat laminated to both sides ofthe electrode. The HDPE is PJX 2242 from Phillips-Joanna of Ladd, Ill.

(E) Cord

One cord, 1 mil diameter TEFLON® coated tungsten wire is placed acrossthe narrow dimension of the gasket and electrode surface and alignedbetween microprotrusions. The location of the cord is one of threepositions centered, left of center, or right of center.

(F) Stacking

Electrode/microprotrusion/gasket/cord/gasket units are stacked beginningwith a 2 mil end plate unit to the desired number of cells and endingwith a plain 2 mil end plate with the cords arranged such that thelocation is staggered-left, center, right in a three unit repeatingcycle (end perspective).

(G) Reflow

The gasket is reflowed in nitrogen at 125° C. for 120 min. to reflow thethermoplastic. The unit is cooled in nitrogen to ambient temperature.

(H) Cord Removal

The cords are removed by pulling the exposed ends to leave the open fillports.

EXAMPLE 3 Fabrication Of Dry Preunit

(A) Coating Method

The support structure is prepared by etching a 1 mil titanium sheet with50% Hcl at 75° C. for 30 min. The end plates are 10 mil titanium.

The oxide coating solution is 0.2M ruthenium trichloride trihydrate and0.2M tantalum pentachloride in isopropanol (reagent grade).

The etched Ti sheets are dip-coated by immersion into the solution atambient conditions. The coated sheet is submerged into the solution,held for about 1 sec and then removed.

After each coating, the oxide is dried at 70° C. for 10 min, pyrolyzedat 300° C. for 5 min and removed to cool to ambient temperature all inambient atmosphere.

The dip-coating steps are repeated for 10 coats (or any desired number)rotating the Ti sheet so as to dip with alternate sides down.

The fully coated sheet is final annealed at 300° C. for 3 hrs in ambientatmosphere.

(B) Electrode Pretreatment

The coated electrode is contacted with saturated steam in a closedvessel at 260° C. for 2 hrs under autogenic pressure.

(C) Spacing

Microprotrusions are screen printed on one side of the electrode, U.S.Ser. No. 947,414 (or photolithographically printed--U.S. Ser. No.958,506). The epoxy compound is EP21AR from Masterbond, Hackensack, N.J.

The epoxy protrusions are cured at 150° C. for 4 hrs. in air. The coatedelectrodes are next die-stamped to the desired shape.

(D) Gasket

A modified high density polyethylene (HDPE, improved puncture resistanceand adhesion) 1.5 mil thick by 30 mil wide with outside perimeter thesame as that of the electrode is placed on the electrodes on same sideas the microprotrusions and impulse heat laminated. The HDPE is PJX 2242from Phillips-Joanna of Ladd, Ill.

(E) Cord

One cord (Tefzel®) 1 mil thick by 10 mil wide is placed across thenarrow dimension of the gasket and electrode surface and aligned betweenmicroprotrusions. The location of the cord is one of three positionscentered, left of center, or right of center.

A second HDPE gasket is placed on the first gasket sandwiching the cordbetween the two gaskets.

The second gasket is impulse heated to adhere to the first gasket and tofix the cord in place.

(F) Stacking

Electrode/microprotrusion/gasket/cord/gasket units are stacked beginningwith a 10 mil end plate unit to the desired number of cells and endingwith a plain 10 mil end plate with the cords arranged such that thelocation is staggered-left, center, right in a three unit repeatingcycle (end perspective).

(G) Reflow

The gasket is reflowed in nitrogen at 160° C. for 45 min. to reflow thethermoplastic. The unit is cooled in nitrogen to ambient temperature.

(H) Cord Removal

The cords are removed by pulling the exposed ends to leave the open fillports.

EXAMPLE 4 Fabrication Of Device

(A) Coating Method

The support structure is prepared by etching a 1 mil titanium sheet with50% Hcl at 75° C. for 30 min. The end plates are 5 mil titanium.

The oxide coating solution is 0.2M ruthenium trichloride trihydrate and0.2M Ti(di-isopropoxide)bis 2,4-pentanedionate in ethanol (reagentgrade).

The etched Ti sheets are dip-coated by immersion into the solution atambient conditions. The coated sheet is submerged into the solution,held for about 1 sec and then removed.

After each coating, the oxide is dried at 70° C. for 10 min, pyrolyzedat 350° C. for 5 min in oxygen and removed to cool to ambienttemperature all in ambient atmosphere.

The dip-coating steps are repeated for 30 coats (or any desired number)rotating the Ti sheet so as to dip with alternate sides down.

The fully coated sheet is final annealed at 350° C. for 3 hrs in anoxygen atmosphere.

(C) Spacing

Microprotrusions are thermally sprayed through a mask on one side of theelectrode. The thermal spray material is TEFLON® from E.I. du Pont deNemours & Co., Wilmington, Del. The TEFLON® protrusions are cured at300° C. for 0.5 hrs. in air. The coated electrodes are next die-stampedto the desired shape.

The microprotrusions are also obtained by photolithography--see U.S.Ser. No. 956,508.

(D) Gasket

A modified high density polyethylene (HDPE, improved puncture resistanceand adhesion) 1.5 mil thick by 30 mil wide with outside perimeter thesame as that of the electrode is placed on the electrodes on same sideas the microprotrusions and impulse heat laminated. The HDPE is PJX 2242from Phillips-Joanna of Ladd, Ill.

(E) Cord

One cord (TEFZEL®) 1 mil thick by 10 mil wide is placed across thenarrow dimension of the gasket and electrode surface and aligned betweenmicroprotrusions. The location of the cord is one of three positionscentered, left of center, or right of center.

A second HDPE gasket is placed on the first gasket sandwiching the cordbetween the two gaskets.

The second gasket is impulse heated to adhere to the first gasket and tofix the cord in place.

(F) Stacking

Electrode/microprotrusion/gasket/cord/gasket units are stacked beginningwith a 5 mil end plate unit to the desired number of cells and endingwith a plain 5 mil end plate with the cords arranged such that thelocation is staggered-left, center, right in a three unit repeatingcycle (end perspective).

(G) Reflow

The gasket is reflowed in nitrogen at 190° C. for 30 min. to reflow thethermoplastic. The unit is cooled in nitrogen to ambient temperature.

(H) Cord Removal

The cords are removed by pulling the exposed ends to leave the open fillports.

EXAMPLE 5 Fabrication Of Dry Preunit

(A) Coating Method

The support structure is prepared by etching a 0.8 mil zirconium sheetwith 1%HF/20% HNO₃ at 20° C. for 1 min. The end plates are 2 milzirconium.

The oxide coating solution is 0.2M ruthenium trichloride trihydrate and0.1M tantalum pentachloride in isopropanol (reagent grade).

The etched Ti sheets are dip-coated by immersion into the solution atambient conditions. The coated sheet is submerged into the solution,held for about 1 sec and then removed.

After each coating, the oxide is dried at 85° C. for 10 min, pyrolyzedat 310° C. for 7 min and removed to cool to ambient temperature all inambient atmosphere.

The dip-coating steps are repeated for 10 coats (or any desired number)rotating the Ti sheet so as to dip with alternate sides down.

The fully coated sheet is final annealed at 310° C. for 2 hrs in ambientatmosphere.

(C) Spacing

Microprotrusions are thermally sprayed through a mask on one side of theelectrode. The thermal spray material is TEFLON® from E.I. du Pont deNemours & Co., Wilmington, Del. The TEFLON® protrusions are cured at310° C. for 1.0 hrs. in air. The coated electrodes are next die-stampedto the desired shape.

The protrusions also obtained using photolithography--see U.S. Ser. No.956,508.

(D) Gasket

A polypropylene gasket 1.5 mil thick by 30 mil wide with outsideperimeter the same as that of the electrode is placed on the electrodeson same side as the microprotrusions and impulse heat laminated.

(E) Cord

One cord, 1 mil diameter TEFLON® coated tungsten wire, is placed acrossthe narrow dimension of the gasket and electrode surface and alignedbetween microprotrusions. The location of the cord is one of threepositions centered, left of center, or right of center.

A second polypropylene gasket is placed on the first gasket sandwichingthe cord between the two gaskets.

The second gasket is impulse heated to adhere to the first gasket and tofix the cord in place.

(F) Stacking

Electrode/microprotrusion/gasket/cord/gasket units are stacked beginningwith a 2 mil end plate unit to the desired number of cells and endingwith a plain 2 mil end plate with the cords arranged such that thelocation is staggered-left, center, right in a three unit repeatingcycle (end perspective).

(G) Reflow

The gasket is reflowed in nitrogen at 195° C. for 60 min. to reflow thethermoplastic. The unit is cooled in nitrogen to ambient temperature.

(H) Cord Removal

The cords are removed by pulling the exposed ends to leave the open fillports.

EXAMPLE 6 Filling Of The Electrode Space

A dry preunit may be filled with an electrolyte with the followingprocedure. Any of many possible dry preunit configurations may be used.

(H) Back Fill

The cords are removed to open the fillport. The stacked unit is placedinto an evacuation chamber and evacuated to <35 mtorr for 5 to 60 min.The liquid electrolyte 3.8M H₂ SO₄ de-airated with nitrogen isintroduced into the chamber and fills the evacuated space between theelectrodes.

(I) Seal Fillport Openings

The electrolyte filled preunit is removed from the chamber. It is rinsedwith deionized water to remove excess electrolyte and dried. HDPE film(1.5 mil thick) is placed over the fillport openings and impulse heatsealed over the ports.

(J) Conditioning

The device is charged up to full charge beginning at 0.1 V/cellincreasing by 0.1 V/cell until 1 V/cell is obtained.

(K) Testing

The device is tested in the conventional manner, having 1 V/cell withleakage current of less than 25 μA/cm², and a capacitance density per acell of greater than about 0.1 F/cm². A 10 V device has a height of nomore than 0.05", a 40 V device has a height of no more than 0.13", and a100 V device has a height of no more than 0.27".

Performance characteristics for various device geometries andconfigurations based on a sulfuric acid electrolyte are presented inTable 1.

                  TABLE 1                                                         ______________________________________                                        Device Performance Characteristics                                            ______________________________________                                        Area/cm.sup.2                                                                          2       2       2     2     25    25                                 volt     10      40      100   100   100   100                                C/mF     26      6.7     2.6   10    150   753                                ESR/mohm 100     330     780   780   62     70                                vol/cc   0.29    0.73    1.6   1.6   11     32                                J/cc     4.5     7.4     8.1   31    69    116                                watt/cc  860     1660    2000  2000  3670  1100                               ______________________________________                                    

EXAMPLE 7 Filling Of The Electrode Space

A dry preunit may be filled with an electrolyte with the followingprocedure. Any of many possible dry preunit configurations may be used.

(H) Back Fill

The cords are removed to open the fillport. The stacked unit is placedinto an evacuation chamber and evacuated to <35 mtorr for 5 to 60 min.The liquid non-aqueous electrolyte 0.5M KPF₆ in propylene carbonatede-airated with nitrogen is introduced into the chamber and fills theevacuated space between the electrodes.

(I) Seal Fillport Openings

The electrolyte filled preunit is removed from the chamber and excesselectrolyte is removed. HDPE film (1.5 mil thick) is placed over thefillport openings and impulse heat sealed over the ports.

(J) Conditioning

The device is charged up to full charge beginning at 0.1 V/cellincreasing by 0.1 V/cell until 1.5 V/cell is obtained.

(K) Testing

The device is tested in the conventional manner, having 1.5 V/cell withleakage current of around 100 μA/cm², and a capacitance density ofaround 4 mF/cm² for a 10 cell device.

EXAMPLE 8 Device Post-Treatment Conditions

The following is a list of the electrical properties (Table 3) ofdevices using various gas postconditioning techniques to adjust theelectrode rest potential so that charging to at least 1 V/cell onmulticell devices filled with 4.6M sulfuric acid electrolyte is possibleand reduced leakage currents are observed. This treatment is donebefore, during, and/or after reflow of the gasket material. For gastreatment at temperatures below that used for gasket reflow theatmosphere was exchanged with an inert gas such as nitrogen or argonduring reflow. For treatment after reflow of the gasket material thetabs were removed before treatment. During treatment the atmosphere isevacuated and filled with the reactive gas periodically.

                  TABLE 3                                                         ______________________________________                                        Device characteristics for various postconditioning.                          gas     T/°C.                                                                         t/min.      i"/μA/cm.sup.2                                                                    V/cell                                      ______________________________________                                        H.sub.2 50      20          8     1.0                                         CO      100    170         40     1.0                                         CO      90     103         12     1.0                                         CO      90     165         20     1.0                                         CO      80     120         25     1.1                                         NO      75      20         27     1.0                                         NO      95     140         21     1.1                                         NH.sub.3                                                                              85      30         26     1.0                                         ______________________________________                                    

EXAMPLE 9 Hot Roller Photolithographic Production of Microprotrusions

The following steps referring to FIGS. 3 and 7-12 are follows:

(A) The ConforMASK® 2000 high conformance solder mask of 1.5 mil inthickness is cut to the same size as the electrode.

(B) The photo resist film 81 is applied to the electrode material byplacing the ConforMASK® film on the electrode material surface 16, afterremoving the release sheet 82 between the photo resist film 82 andelectrode 16, and passing the laminate through heated rollers (84 and85) (at 150° F.) to adhere the photo resist film 81 to the electrodesurface 16. The polyester cover sheet 82A on the outside of the photoresist film 81 is then removed.

(C) The dark field mask 87 containing rows of transparent holes(openings 88) is placed on the photo resist 81. A typical patternconsists of an array of holes 6 mil in diameter 40 mil center-to-centerspacing with a higher density (20 mil center-to-center) for three rowson the perimeter of the electrode.

(D) The film 81 is exposed through holes 88 the mask 87 for 20 secondsto a conventional UV light source, 89 a mercury vapor lamp. The mask isremoved.

(E) The unexposed area of the photo resist is developed or stripped byplacing it in a tank with 1% potassium carbonate for 1.5 min.

(F) The electrode surface 16 with the microprotusion standoffs 13 isthen washed with de-ionized water, placed in a tank with 10% sulfuricacid, for 1.5 min and a final de-ionized water rinse.

(G) First, the microprotrusions 13 are exposed to UV light. A final cureof the microprotrusions (standoffs) is done in a convection air oven at300° F. for 1 hr.

The finished electrode is used directly or treated as described hereinor in the pending parent or incorporated by reference applications.

EXAMPLE 10 Vacuum Lamination of Photo resist

(A) The ConforMASK® 2000 high conformance solder mask of 2.3 mil inthickness is cut slightly larger than the electrode.

(B) The photo resist film is vacuum laminated to the electrode materialand onto a supporting backing plate using standard operating conditions(160° C., 0.3 mbars) using a Dynachem vacuum applicator model 724 or730. The polyester cover sheet is removed.

(C) The dark field mask containing rows of transparent holes is placedon the photo resist. A typical pattern consists of an array of holes 6mil in diameter 40 mil center-to-center spacing with a higher density(20 mil center-to-center) for three rows on the perimeter of theelectrode.

(D) The film is exposed for 20 to 40 seconds to a non-collimated UVlight source of 3-7 KW power.

(E) The unexposed area of the photo resist is developed or stripped byusing 0.5% potassium carbonate in a conveyorized spray developing unit,followed by a de-ionized water rinsing and turbine drying.

(F) A final cure of the standoffs is done in a two step process. First,the microprotrusions are exposed to UV light in a Dynachem UVCS 933 unitand then placed in a forced air oven at 300°-310° F. for 75 min.

The finished electrode is used directly or further treated as describedherein and in the pending parent applications.

The device produced by the methods described in the claims have uses asan electrical source of power for applications independently selectedfrom:

providing peak power in applications of varying power demands and berecharged during low demand (i.e. serving as means for a powerconditioner, placed between the electrical generator and the electricalgrid of the users;

providing power in applications where the electrical source may bediscontinued and additional power is needed to power in the interimperiod or for a period to allow for a shutdown providing means foruninterruptable power source applications, comprising computer memoryshutdown during electrical grey and brown outs, or power during periodicblack outs as in orbiting satellites;

providing pulse power in applications requiring high current and/orenergy comprising providing means for a power source to resistively heatcatalysts, to power a defibrillator or other cardiac rhythm controldevice, or to provide pulse power in electric vehicle where in a batteryor internal combustion engine could recharge the device;

providing power in applications that require rapid recharge withprolonged energy release comprising surgical instruments with out anelectrical cord; or

providing a portable power supply for appliance and communicationapplications.

Coating of Support Material

The coating (e.g. oxide) is porous and composed of mostly micropores(diameter<17 Å). Large 0.1-1 μm wide cracks are present on the surfaceprotruding to depths as thick as the coating. However, greater than 99%of the surface area arises from these micropores. The average diameterof these micropores are around 6-12 Å.

After various post-treatments the pore structure can be altered toincrease the average pore size. For example, the steam post-treatmentcreates a bimodal pore distribution. In addition to the micropores, anarrow distribution of mesopores (diameter<17-1000 Å) having a diameterof about 35 Å is created. These treated electrode coatings have 85-95%of the surface area arising from the micropore structure.

With alternate electrode construction methods this pore sizedistribution can be varied. The effective high surface area of thecoating is 1000 to 10,000 to 100,000 times larger than the projectedsurface area of the electrode as a monolith. The pore size,distribution, and surface area controlled with the temperature ofpyrolysis and/or high temperature water treatment. In addition, the useof surfactants to create micelles or other organized structures in thecoating solution increases the average pore size up to values about100-200 521 with only 5-10% of the surface area coming from micropores.

As illustrated in FIG. 13, the electrode 111A includes a porous andconductive coating layer 119, which is formed on at least one surface ofthe support material 116. The support material 116 is electricallyconductive, and sufficiently rigid to support the coating layer 119 andto impart sufficient structural rigidity to the device 10.

One goal of the present invention, is to optimize the energy density andpower density of the device 10. This object is achieved by reducing thethickness of the support material 116, and maximizing the surface areaof the coating layer 119. The power density of the device 10 is furtheroptimized, by maintaining a low resistance.

The surface area of the coating layer 119 is determined by the BETmethodology, which is well known in the art. The surface enhancement,which is an indication of the optimization of the surface area of thecoating layer 119, is determined according to the following equation:

    Surface enhancement=(BET Surface Area/Projected Surface Area)

In the present invention, the surface enhancement values are as large as10,000 to 100,000, and are usually greater than 50.

The coating layer 119 is porous, and its porosity could range betweenabout five percent (5%) and ninety-five percent (95%). Exemplaryporosity range for efficient energy storage is between about twentypercent (20%) and twenty-five percent (25%). The porous coatingthickness is between about 1 and 200 micron, preferably between about 5and 50 micron.

In conventional double-layer capacitors, the main device resistance isdue to the carbon coating layer. In the present invention, most of thedevice resistance is due to the electrolyte, which has a higherresistance than that of the porous conductive coating layer.

While only a few embodiments of the invention have been shown anddescribed herein, it will become apparent to those skilled in the artthat various modifications and changes can be made in thephotolithographic formation and applications of microprotrusions toprovide substantially uniform spacing between electrodes of anelectrical storage device without departing from the spirit and scope ofthe present invention. All such modifications and changes coming withinthe scope of the appended claims are intended to be carried out thereby.

What is claimed is:
 1. A photolithographic method to producemicroprotrusions which are substantially uniform in height on a poroussubstrate to maintain space separation between electrodes in anelectrical storage device, which method comprises:(a) obtaining anunexposed photoresist film which is essentially inert to subsequentelectrolyte conditions and is electrically insulating when cured; (b)obtaining a thin electrode material comprising a thin flat electricallyconducting metal sheet coated on one or both flat sides withelectrically conducting porous metal oxide or electrically conductingcarbon; (c) applying the photoresist film to one or to both flat sidesof the electrode material; (d) placing a mask having a plurality ofsmall holes over the photoresist; (e) exposing the photoresist to alight source of an intensity and for a time effective to substantiallycure the light exposed photoresist material through the holes in themask such that the photoresist material through the holes are exposed toabout a uniform amount of light to create substantially curedmicroprotrusions of about uniform height followed by removing the mask;(f) developing the photoresist film to leave the substantially curedmicroprotrusions on the surface of the electrode material and to removeunreacted film; and (g) further curing the remaining exposedsubstantially cured microprotrusions whereby the microprotrusions ofsubstantially uniform height essentially retain their shape anddimensions.
 2. The method of claim 1 wherein the device is selected fromthe group consisting of a capacitor and a battery.
 3. The method ofclaim 2 whereinthe electrically conducting porous metal oxide is anelectrically conducting high surface area material selected from mixedmetal oxides; the electrode material is independently selected from thegroup consisting of titanium, zirconium, nickel, aluminum and alloysthereof; and the photoresist is a commercial solder mask.
 4. The methodof claim 1 wherein the electrically conducting porous metal oxide orcarbon is an electrically conducting high surface area material.
 5. Themethod of claim 4 wherein the electrically conducting high surface areamaterial is substantially composed of carbon.
 6. The method of claim 4wherein the electrically conducting high surface area material isselected from the group consisting of a metal oxide and a mixed metaloxide.
 7. The method of claim 6 wherein the mixed metal oxide isindependently selected from the group consisting of ruthenium, titanium,tantalum, chromium, iridium and combinations thereof.
 8. The method ofclaim 1 wherein in step (c) the photoresist film is applied to one sideof the electrode material andin step (d) the mask is laminated over thephotoresist using a hot roller pressure technique at between about 100°to 200° F.
 9. The method of claim 8 wherein the temperature is about150° F.
 10. The method of claim 1 wherein the photoresist film comprisesan organic photo-curable epoxide polymer, an organic photo-curableacrylate polymer or combinations thereof.
 11. The method of claim 1whereinin step (b) the metal oxide coats both sides of the electrode, instep (c) the film is applied to one flat side using a hot rollertechnique, in step (f) developing occurs using dilute aqueous base andin step (g) using light, heat or a combination thereof to further curethe microprotrusions.
 12. The method of claim 1 wherein in step (c) thephotoresist is applied by vacuum lamination.
 13. A photolithographicmethod to produce microprotrusions which are substantially uniform inheight on a porous substrate to maintain space separation betweenelectrodes in an electrical storage device, which method comprises:(a)obtaining an unexposed photoresist film which is essentially inert tosubsequent electrolyte conditions and is electrically insulating whencured; (b) obtaining a thin electrode material comprising a thin flatelectrically conducting metal sheet coated on one or both flat sideswith electrically conducting porous metal oxide or electricallyconducting carbon; (c) applying the photoresist film to one or to bothflat sides of the electrode material; (d) placing a mask having aplurality of small holes over the photoresist; (e) exposing thephotoresist to a light source of an intensity and for a time effectiveto substantially cure the light exposed photoresist material through theholes in the mask such that the photoresist material through the holesare exposed to about a uniform amount of light to create substantiallycured microprotrusions which are substantially uniform in heightfollowed by removing the mask; (f) developing the photoresist film toleave the substantially cured microprotrusions on the surface of theelectrode material and to remove unreacted film; and (g) further curingthe remaining exposed substantially cured microprotrusions whereby thesubstantially uniform in height microprotrusions essentially retaintheir shape and dimensions, wherein in step (b) the flat metal sheet isselected from titanium, zirconium, iron, copper, lead, tin, nickel, zincor combinations thereof, having a thickness of between about 0.1 and 10mil, and the metal sheet is coated on each flat surface with a thinlayer of at least one metal oxide having a high surface area which metaloxide is independently selected from metal oxides from the groupconsisting of oxides of tin, lead, vanadium, titanium, ruthenium,tantalum, rhodium, osmium, iridium, iron, cobalt, nickel, copper,molybdenum, niobium, chromium, manganese, lanthanum, other metals of thelanthanum series and combinations thereof, and said thin metal oxidelayer has a thickness of between about 0.1 and 100 microns.
 14. Themethod of claim 13 wherein in step (d) the mask is laminated over thephotoresist using a hot roller technique at between about 150° to 200°F.
 15. The method of claim 14 wherein the temperature is about 150° C.16. The method of claim 13 wherein the photoresist film comprises anorganic photo-curable epoxide polymer, an organic photo-curable acrylatepolymer or combinations thereof.
 17. The method of claim 16 wherein thephotoresist is an organic photo-curable epoxide polymer.
 18. The methodof claim 13 wherein the metal oxide is a mixed metal oxide, and thephotoresist is a negative working photopolymer.
 19. The method of claim13 wherein the mixed metal oxide has an electrically conducting highsurface area.
 20. The method of claim 13 wherein in step (b) only carbonin particle form is coated on the electrically conducting materialsheet.